Just an update regarding international FW on Chinese version of Yi 4k. It is possible, and it is easy
How to Change Chinese Firmware To English
1. Download the YI4k Beta Live file and Extract
here or
here
2. Access folder and find the file “firmware_force.bin”
3. Copy and Paste it into your Memory Card, dont rename it! (Memory Card must be formatted in FAT32. Recommended card speed is at least U3. i.e Sandisk Extreme Pro u3)
4. Insert memory Card into your Yi4k Action Camera, turn on your camera and let it update for a minute. (Battery should remain at least 50% to perform this update)
5. After successfully updated, Turn off and Turn on one time.
6. Enjoy your Yi4k
Note: This is only beta version. Please do not perform any updates, or else your camera may be bricked
All credits goes to guy who made this vid:
I just did this method on two Yi 4k, and it works without any problem. No "illegal version" message